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| Author | Topic: Medical Tube Extrusion |
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ronvieky Member Posts: 3 |
posted April 14, 2009 12:51 AM
  
Hi everyone, I am new to the forum, and new ot the plastics Industry. 1>Can anyone tell me why do plastic tubes require smaller machines for Extrusion? Why can't we have multiple heads on a bigger machines, and extrude 4 tubes from the same machine, and same material. 2> Does anyone know how ot select the right Die-torpedo design for the right Tubing? I know that tubing OD and ID can be set by controlling the traction control / the pulley arrangement. But there's only a slight margin of tubes that can be extruded from 1 Die-torpedo. the rest is controlled by the Traction conveyor. Is there a formula to calculate the right Die and torpedo set to tubes? 3> Why is the screw RPM limited for tube extrusion? What's the limiting factor in Tube extrusion for maximum throughput. Screw RPM can go upto 150 RPM. still, the tubes are extruded at an extremely low rpm as compared to the machines capacity. Why is that? Will buying a better-faster-stronger traction Controller increase the output? or is it unavoidable for small OD tubes (say 1.98mm - to - 6.6 mm. OD) to be extruded at lower RPMs. Is there any formula for calculating the Maximum RPM the tubes can be extruded at with including all factors : traction controller line speed, Screw dia, OD-thickness of Tubes extruded, and etc etc. 4> What about Screw design? For extruding PVC tubes, with a Maddok design, L/D=24. Is there a posiblity of further increasing productivity based on screw design? If yes, can you please explain in brief, how they are related? 5> Is there any book for Tube/Profile Extrusion? for either medical purpose, or general. But it can give me more insight on the subject. Looking forward to your reply. Thanks. IP: Logged |
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Tom C Moderator Posts: 923 |
posted April 14, 2009 01:16 PM
Extrusion limits: Product cooling There are genralized design rules available for tubing dies. Multiple dies can be run, but it requires careful engineering. The only peice that does not need to be duplicated is the extruder.
Tom Cunningham [This message has been edited by Tom C (edited April 14, 2009).] IP: Logged |
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Stephen J. Derezinski Senior Member Posts: 88 |
posted April 26, 2009 04:10 PM
I think that the precise wall-thickness and uniformity needed by the tiny medical tubing makes keeping the extrusion line symetrical. That is, the centerline of the tubing is the same as the extruder. Radial variations in melt are most uniformily distributed in the tubing with this arrangement. Also, slow rpm of the extruder will provide for uniform product temperature, so long as excessive barrel heating is not needed to reach the product temperature. In general, excessive barrel heating will occur if the screw is too short. ------------------ IP: Logged |
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